Petroleum conversion process



C. E. HEMMINGER PETROLEUM CONVERSION PROCESS oct.v 3o, 1945.

Filed Julie 13, 1942 Newz@ Patented Oct. Si), 1945 PETROLEUM CONVERSIONPROCESS Charles E. Hemminger, Westfield, N. J., assgnor to Standard OilDevelopment Company, a corporation of Delaware Application June 13,1942, Serial No. 446,850

7 Claims.

The present invention relates to improvements in the art of treatinghydrocarbons and, more particularly, it relates to the preparation offeed stocks for cracking operations.

Prior to my present invention, it has been the practice to subject aheavy hydrocarbon oil such as a reduced crude, to viscosity reducing orto coking in order to convert substantial quantities of the reducedcrude to lower boiling fractions, particularly gas oil, which aresuitable feed stocks for catalytic cracking or thermal cracking. Morerecently, however, there have been processes developed for convertingreduced crudes or even whole crudes in a single operation to gasoline.In this type of operation the crude is heated up to a temperature of say900 F. or 1000 F. and then injected in liquid form into a reactor whereit contacts a mass of powdered catalyst. In the preferred type ofoperation, the catalyst is in the form of a luidized mass or extremelydense suspension and is adapted to be continuously withdrawn from thereactor, regenerated and recycled to the said reactor. When using highcatalyst to oil weight ratios and making use of the heat content of thecatalyst recovered from the regeneration zone, it is possible to effectthe desired conversion of heavy stocks into substantial quantities ofgasoline of high octane number, even though the charging heavy oil ismerely preheated to temperatures considerably below crackingtemperatures and in some cases where the fresh feed is fed into thereaction zone at ordinary atmospheric temperatures. It is obvious thatthis type of operation presents numerous advantages, since in aone-stage operation gasoline of high octane number is obtained,particularly Where the catalyst is an active one such as an acid treatedmontmorillonite clay or the like, or a synthetic catalyst such as amixture of silica and alumina or silica and magnesia gels.

In my prior application, Serial No. 363,866, led November 1, 1940, andentitled Viscosity reducing, I have described a method for treatingheavy stocks in a continuous operation where I inject the heavy oil intoa conversion'zone Where itis converted to hydrocarbons boiling withinthe gas oil and gasoline ranges, and I have pointed out in saidapplication that where an active cracking catalyst is present in theconversion zone, I obtain a gasoline of improved octane number.

I have now found that in treating some stocks it is not alwayspreferable to convert the Vheavy stocks in a single stage operationdirectly to gasoline, but rather it is best to rst convert the heavy oilinto substantial quantities of hydrocarbons boiling higher than thegasoline range and then without substantial cooling to conduct theformed gas oil to either a catalytic cracking operation or a thermalcracking operation Where the cracking of the gas oil may be effected. Iconsider it one of the advantages of my present invention, therefore,that by treating the heavy oil in two stages, that is rst subjecting itto viscosity reducing and then cracking the formed gas oil in a separatestage, I may more accurately control the actual product of the crackedgasoline so as to improve the quality, the yields, and the productdistribution.

One object of my invention therefore is to subject a heavy petroleumhydrocarbon oil, such as a reduced crude to a viscosity reducingoperation in a conversion zone where the conversion is carried outcontinuously in the presence of a powdered material, to recover vaporscontaining substantial quantities of gas oil from said conversion zone,and then to crack these gas oil vapors without substantial cooling in aseparate cracking zone where preferably an active cracking catalyst i ispresent.

It is a further object of my present invention to employpowderedpetroleum coke in the vis- Y cosity reduction of a heavy petroleum oilin an operation which is conducted continuously since I thereby recoverthe coke formed in the viscosity breaking and avoid degradation of thecharging stock to excessive quantities of coke and improve the overallproduct distribution to increase the yields of desired constituents,principally gas oil.

It is a still further object of my invention to carry out a combinedviscosity reducing operation and a cracking operation under suchconditions as to conserve heat.

It is a still further object of my invention to carry out the combinedviscosity reduction of a heavy petroleum hydrocarbon oil and cracking ofgas oil formed in the viscosity reducing operation in an operation whereheat is conserved and other conditions are so adjusted as to make theentirev system substantially internally self-sustaining as to heatrequirements.

Other and further objects of my invention will appear from the followingmore detailed description and claims.

In the accompanying drawing, 1 have shown diagrammatically thecombination of apparatus elements in which a preferred modification ofmy invention may be carried into practical effect.

I shall now set forth in detail a specic example illustrating myinvention, with the understanding that the precise details hereinafterenumerated are purely illustrative and that it is to be understood thatthe following details of operation do not impose any limitation on myinvention.

In setting forth the said example, I shall refer to the drawing.Referring in detail to the drawing I represents a charging line intowhich a heavy petroleum hydrocarbon oil, such as a reduced East Texascrude oil having an A. P. I. gravity of say about 18, is introduced intothe system and thence pumped by.pu'mp 3 directly into a viscosityreducing reactor containing, as will hereinafter more fully appear, afluidized mass of powdered coke, which coke is in the form of a densesuspension having an upper level substantially at L and being maintainedin this condition by a gasiform material which passes through 5 at aslow enough rate to maintain the coke in the iiuidzed condition referredto. The coke may be maintained in this condition when it is ground to asize of from 100-400 mesh by forcing a gasiform material upwardlythrough the reactor at a linear velocity of say 0.3-5 ft. /second. Underthese conditions the coke, as indicated, forms a dense suspension which,however, is not to be confused with the ordinary conception of asuspension which usually means that a solid is suspended in a gas movingat a velocity sufficiently high to cause substantially concurrentmovement of solid and gas. In my reactor 5, thel velocities are muchlower so that there is a slippage of solid with respect to gas, and thefinal result is that the mass of coke is in a turbulent, ebullientcondition resembling roughly a boiling liquid. More details of themanner of injecting the coke in the reactor 5 will be suppliedhereinafter. 'At this point it will merely be pointed out that the cokeis preferably maintained at a sufciently high temperature so that whencold or heated oil is discharged from I into the reactor, the cil isheated up to a temperature" of 850- 1200 F. This temperature maybeacquired by maintaining a high weight ratio of coke to oil where thecoke is at an inlet temperature of say 100G-1100 F., up to 1300 F. Theoil remains resident in the vessel 5, which is maintained under apressure just suliicient to overcome pressure ,drops inthe subsequentportions of the apparatus and may be of the order of -50 lbs gauge for asuiiicient period of time to form vaporized products containinga minimumof gasoline and tar and/or coke, the latter being absorbed by the cokepresent in the reactor.

'I'he vapors released during the conversion pass upwardly and arewithdrawn through line ID andl thence discharged into a cycloneseparator I2. The vapors in line I0 contain comparatively smallquantities of coke because conditions are so maintained that there isabout a 10-20 ft. disengaging space from L to the outlet pipe I0.

Therefore, whereas the mass below L may have a density of from say 10-40lbs./cu. ft., the vapors in line I0 under best operating conditions willhave a density of the order of say 0.01 to 0.001 lbs/cu. ft. The nes areseparated in cyclone separator ,I2 and then returned through line I4 tothe coking vessel. The overhead vapors, on the other hand, are withdrawnthrough line I6 and since they are at a temperature of about 850-1200F'. they may be discharged directly into a cracking vessel I 8containing a cracking catalyst also in the form of a dense suspensionhaving an upper level at L', the mass of catalyst being intermixed withthe hydrocarbon vapors to form the same sort of iluidized mass as ispresent in reaction vessel 5. For example, the catalyst which may be anacid treated clay or a synthetic catalyst such as a mixture of silicaand alumina or silica and magnesia gels, or other known catalysts ispreferably in the form of a powder having a particle size of from20D-400 mesh, and the ilow of vapors upwardly through reaction vessel I8is so regulated as to linear velocity, that it is somewhere between0.3-5 ft. per second as to give a dense suspension or turbulent,ebullient mass of catalyst intermixed with the vapors. The heated vaporsare in contact with the catalyst for a sucient period of time to effectthe desired conversion which usually is a matter of say l0-l5 or 20seconds, and the reaction products are withdrawn overhead through line20 and discharged into a cyclone separator 24 where the rines areseparated and returned to the reactor through line 30. As before, thevapors in line 20 contain only a very small amount of catalyst ifdisengaging space between L and the top of reactor is of the order of l2ft. even where the density of the mass below L' is as high as from 10-40lbs. per cu. ft.

In reactor I8, since the total vapors from 5 are reacted therein andsince these vapors contain a small quantity of gasoline, as well as alarger quantity of gas oil, the gasoline fraction will be cracked, but:this cracking would serve to improve the quality of the gasoline,particularly as regards its octane number. -The gasoline produced alongwith the gas oil will also have a good octane number and finally thenormally gaseous products which are present will undergo polymerizationand/or isomerization of paraflins, with possibly some alkylation, sothat the products withdrawn from cyclone separator 24 through line 32and subsequently discharged into a fractionator 35 will contain agasoline fraction of good quality. The vapors in fractionator 35 arefractionated into two fractions, namely, an overhead product which iswithdrawn through line 4I, passed through a condenser 43, thencewithdrawn through line 5I 'and discharged into receiving drum 53. Fromreceiving drum 53, the lighter hydrocarbons are withdrawn through a.line 5B and compressed in a compressor 5l to about 200 lbs/sq. in., or,in other words, sufciently high to liquefy not only the C5 but also theC4 hydrocarbons, or at least a major portion of them. The bottoms fromdrum 53 are withdrawn through line 55 and these are also pumped intoreceiving drum 6U. The liquid product consisting of gasoline iswithdrawn as product through line 6I. The overhead from drum 60 iswithdrawn through line 62, and this overhead consists essentially of C3and lighter hydrocarbons which may be recycled to line 40 to aid in theliuidizing of the solid material in reactor 5, and also to aid inrepressing the formation of C3 y and lighter gas from the charging oilduring the reaction.

Referring again to viscosity reducing drum 5, coke is continuouslywithdrawn through the draw-off pipe 'Ill and preferably is dischargedinto an injector l2 where it is admixed with air also discharged intosaid injector through line 15. In the injector l2, a suspension of thepowdered coke in air is formed, and this suspension is withdrawn throughline 16. Instead of using injector 'I2 some other suitable mixing devicemay be employed. The suspension in line I6 is then discharged into ahigh speed upiiow reactor 80, that is to say, it is discharged into areactor 8U where it flows upwardly at a linear velocity of about 2-10ft./second, producing a suspension in 80 which is substantiallydifferent from that ot 5 or I8, in that it is less dense, weighing sayfrom 5-20 lbs/cu. ft. and in which suspension there is much less delayedsettling or slippage. In vessel 80, which is in effect a combustionzone, the coke or tar formed in the vessel 5 is burnt, together withsome of the original coke, although the amount of the latter which isburnt is preierably limited. Since the coke withdrawn from viscosityreducer 5 is at a temperature of 850- 1200 F., the air discharged intothe system through line 'I5 need not be heated .to cause activecombustion in vessel 80Uand the entering air may be at atmospherictemperatures. The revlviiied coke is withdrawn from combustion zone 80through line 85 and thence discharged into a cyclone separator 86 inwhich the coke is separated from the flue gases and discharged throughline 90 into the coking vessel 5. Flue gases, on the other hand, arewithdrawn from cyclone separator 86 through line 92, and these gases maybe sent to other dust separators or the like to recover additional coke,but preferably they are discharged directly into a waste heat boiler(discussed later) to recover a portion of their sensible heat.

Due to the viscosity breaking or light pyrolysis of the heavy reducedcrude there will be a substantial formation of carbon in reactor 5 onthe hot recycled coke. It is the purpose of this invention to build upthis carbon on the coke so as to reduce the deposit of coke on thecatalyst in vessel I8 and to recover it as a solid carbon. For thispurpose powdered coke is withdrawn from the system through line 'II soas to keep the coke inventory in the system constant. After cooling itis a saleable product for a solid fuel, electrodes, carbon bricks andother uses. This coke can also be withdrawn through line 9| from line00. In the case of line the coke is wet because it contains morevolatile hydrocarbons than the material from line 90.

Mention should be made that the recovery in 4 the cyclone I2 andauxiliary recovery equipment need not be complete because coke particlespassing through line I6 are recovered in vessel I0 and burnt in vessel|20. As such they add heat to the cracking system and by controlling thecarbon in line I6 the heat balance in the cracking system may be alteredor controlled.

The coke in line 90, due to its passage through combustion zone 80, willnormally have its temperature increased a few hundred degrees so that asit re-enters vessel 5 it will have a temperature of 1000l-1300J F. orhigher. Aspreviously indicated, by using a high ratio of coke .to inletoil, the superheat of the coke will serve to supply the heat necessaryin reaction vessel 5, thus tending to make the coking phase of myoperation self-sustaining with respect to heat requirements, as ispreviously indicated.

The catalyst in reaction vessel I8 is continuously withdrawn throughline |00 and discharged into an injector I02 where it is mixed with airor some other oxygen-containing gas to form a suspension of catalyst,which is fouled in cracker IB, with air. This suspension is withdrawnthrough line I|0 and thence discharged into a regeneration vesse1 |20,which is preferably of the high speed upflow type, vsimilar' tocombustion vessel 80. The catalyst which is at a temperature of aboutsay 850 drawn from reaction vessel I8 may be mixed with air, and thismixture when discharged into F. or l200 F. as it is withvessel |20 willcause combustion of. the contaminants on the catalyst to restore theactivity of the latter. The suspension will move concurrently upwardwith respect to air and catalyst, in vessel |20 during the combustion ofthe said contaminants, and the suspension is then withdrawn through line|25. As in the case of combustion zone 80, the total catalyst is takenof! overhead which, as previously indicated, is possible when thesuspension moves at a velocity of about 2-10 ft./second where thecatalyst is in a particle size of from -400 mesh or thereabouts. Thesuspension is then discharged into cyclone separator |30 where thecatalyst is separated from the ilue gases and returned to cracker I8through line |35. This catalyst normally would be at a temperature of1050-1300 F.. as it enters the cracker I8, and here also by using a highcatalyst to oil ratio, that is to say, using 5-20 lbs. of catalyst perpound of oil, the cracking reaction taking place in I8 may bei fullysatisfied as to heat requirements by the sensible heat of the catalyst.Since, of course, in this case the entering oil is not cold anddepending on the temperature of the oil vapors in line I6, the amount ofcatalyst may be reduced and of proportion to maintain in vessel I8. Theue gases are withdrawn from cyclone separator |30 through line |40, andordinarily these gases are passed through two or more additionalcyclones and/ or electrical precipitators to remove the last traces ofcatalyst, and thereafter the gases may be mixed with the gases in line92 and sent to some heat recovery system.

The mixing of the iiue gases in lines 92 and |60 and the passage towaste heat boiler |02 after introduction of air at line IM, is animportant phase of this invention. The potential and sensible heat inthese gases are recovered by burning in the boiler |42, giving heat towater introduced through |44 to produce steam in |45, the cooled iiuegases leaving through |03. Of course, other uses as for heating oil canbe made of this heat in suitable furnaces.

The flue gases in |40 from vessel |20 contain combustibles in the formof CO and slight traces of Hz-i-CH4. The CO to CO2 ratio may be as highas 1 to l, giving a heat content of about 15 to 25 B. t. 11./cu. ft. Dueto the low concentration of the combustibles and the low temperaturethey do not burn in the presence of oxygen and the heat is notrecoverable. However, the u addition of the hotter gases, usually 50-100F.

hotter, from vessel 00 through line 92 along with the powdered coke andhydrocarbon gases therein makes possible the combustion of the CO fromvessel |20.

Another feature of this heat recoverysystem is that it allows theconversion of part of the coke formed in viscosity breaking in vessel 5into useful heat in the form of steam. By regulating the recovery of thecoke in cyclone 86 and auxiliary equipment, more or less of the coke canbe withdrawn from the coke circulatory system. This withdrawn portion isthe iiner part and as such is a means'of regulating the neness of thecoke circulating stream. The withdrawal of this coke also cheapens andsimplifles the recovery system 86. In fact, if desired, all of the cokeformed in the viscosity breaking can be withdrawn through line 92 andburned to generate steam in boiler |42 as an integral part of theviscosity breaking system.

If desired, a cyclone or other recovery system the proper temperaturelevel l.,

may be added |45, |48, |41 after the boiler |42. Then, the combustion inboiler |42 is limited so that unburnt carbon is recovered in cyclone|45'. This carbon will be dry, that is, contains little volatilehydrocarbons, and as such is a more valuable product than the carbonwithdrawn from lines 7| and 9|.

It is believed to be obvious that many modiiications of my inventionwill readily suggest themselves to those skilled in this particular art.For example, instead of using petroleum coke in viscosity reducingvessel 5, I may use some other material such as pumice, or I may use anactive cracking catalyst such as an acid treated clay, although I preferto limit the operation taking place in reaction vessel to the productionof a maximum quantity of gas oil which I subsequently employ as a feedstock to a cracking operation. With respect to the cracking operation,while I have disclosed a catalytic operation, it will be understood thatI may thermally crack the gas oil in cracker I8 at high temperatures inthe presence of steamy and by this means secure a gasoline product ofimproved quality. In this modiication of my invention, it is preferableto discharge into cracker |8 1 to 10 or more parts by weight of steam,say at a temperature of 1800-2200 F. per part of oil vapors, in whichcase I may produce a gasoline of improved octane rating which would makea satisfactory base stock from which aviation i-uel may be made byadmixing therewith an alkylate, that is, a liquid product produced, forexample, by alkylating isobutane with butylene. It will be furtherunderstood that the superheat of the ue gases in lines 92 and |40 may beemployed to preheat the oil entering the system through line I, in whichcase a lesser quantity of hot coke would have to be recirculated tovessel 5 to maintain the viscosity reducing operation.

It will be understood, also, that where I have shown fractionatingequipment that the said fractionator is provided with the usualreboiling and reiluxing equipment, although they are not specificallyshown in the drawing. These details of construction and operation arewell known in the art.

While I have shown reactors 5 and i8 to be the bottom drawoiT type, thatis, where the bulk of catalyst is drawn oil from the bottom through thestandpipe, it is to be understood that it is within the scope of myinvention to employ reactors where the bulk of the material is withdrawnoverhead as, for example, in regenerators 80 and |20; and by the sametoken, in my invention I may operate regenerators 80 and |20 in the samemanner as 5 and 8 are operated, namely, by dra-wing oi the bulk of thepowdered material from the bottom of the said regenerator.

It is my intention to claim all of the matter specically disclosedherein and also that which is inherent by necessary implication, exceptthat excluded by the terms of the appended claims.

What I claim is:

l. The method of producing gasoline from reduced crude petroleum oil ina two-stage operation which comprises first discharging the oil into aheated fiuidized mass of powdered coke in cooled into a iluidized massof heated cracking said vapors to remain in contact with the heatedcatalyst for a. suiilcient period of time to convert a substantialportion of the gas oil into gasoline, withdrawing the reaction productsfrom contact with the said catalyst recovering therefrom a gasoline ofimproved quality and withdrawing both the coke and the catalyst from theviscosity reducing zone and the cracking zone respectively, causingcombustion in the presence of air of combustibles associated with thecoke and said catalyst in said zones whereby the temperatures of boththe coke and the catalyst are increased, and returning the coke andcatalyst to the viscosity reducing zone and the cracking zonerespectively in suillcient quantity to maintain reactions as regardsheat requirements in said zones.

2. A continuous method for producing gasoline from a relatively heavyhydrocarbon oil in a multi-stage operation which comprises dischargingthe heavy cosity reducing zone and said cracldng zone. respectively,separatelysubjecting said petroleum coke and said fouled catalyst to theinfluence of an oxygen-containing gas at temperatures sumcientlyelevated to cause combustion of the carbonaceous contaminants, andthereatjter returning substantially uncooled the petroleum coke to theviscosity reducing zone andthe regenerated catalyst to the crackingzone.

6. The method set forth in claim 5 in which the powdered coke in theviscosityreducing zone and the catalyst in the cracking zone aremaintained in dense suspension by causing a gasiform material to ilowupwardly through said zones at a linear velocity within the range ofabout 0.3-5 1t./second.

'1. The method set forth in claim 5,-in which the catalyst to oil ratiois such as to maintain the vapors in the cracking zone at reactiontemperatures without the use of extraneous heat. l CHARLES E.-HEMll/IINGER.

